Papillomaviruses cause benign and malignant epitheliomas in vertebrates, and are grouped into genera of related viruses. Alpha genus HPV's cause anogenital and head and neck cancers that arise from the influence of the virally encoded E6 and E7 oncoproteins. Beta genus HPV types are associated with cutaneous squamous cell carcinomas in immunosuppressed patients, and other HPV types can cause disabling warts in immunosuppressed and HIV infected persons. The action of the virally encoded E6 oncoprotein is critical for the production of both benign epitheliomas and cancers in all HPV types, and the cancer phenotype can be inhibited if E6 expression is inhibited. Therefore, an understanding of the structure of E6 and how E6 interacts with its cellular targets is critical to potential interventions. In the first award cycle of this renewal application, we defined the three dimensional molecular structure of E6 proteins bound to their cellular targets, which is a finding that had been sought for decades. In addition, this application elucidated a newly described cellular target of beta genus E6 called MAML1. MAML1 is a transcriptional coactivator of Notch signaling, so discovery of this association is an important advance in understanding the biology of both human (MAML is the target of E6 proteins in the beta and mu genera) and animal E6 proteins. When E6 proteins bind their cellular targets (called LxxLL docking motifs in the target protein), they undergo an allosteric change in shape to interact with additional proteins such as the p53 tumor suppressor. In this renewal application, we will extend the analysis of E6 structure to additional E6 proteins of medical importance, determine at the molecular level how E6 interacts with additional cellular proteins such as the p53 tumor suppressor, and determine the surface domains of E6 that are required for critical aspects of the papillomavirus life cycle.